InGaAlAs Quantum Wells Research Articles

Direct measurement of the spectral dependence of Lamb coupling constant in a dual frequency quantum well-based VECSEL.

Spectral dependence of Lamb coupling constant C is experimentally investigated in an InGaAlAs Quantum Wells active medium. An Optically-Pumped Vertical-External-Cavity Surface-Emitting Laser is designed to sustain the oscillation of two orthogonally polarized modes sharing the same active region while separated in the rest of the cavity. This laser design enables to tune independently the two wavelengths and, at the same time, to apply differential losses in order to extract without any extrapolation the actual coupling constant. C is found to be almost constant and equal to 0.84 ± 0.02 for frequency differences between the two eigenmodes ranging from 45 GHz up to 1.35 THz.

Hybrid grating reflectors: Origin of ultrabroad stopband

Hybrid grating (HG) reflectors with a high-refractive-index cap layer added onto a high contrast grating (HCG) provide a high reflectance close to 100% over a broader wavelength range than HCGs. The combination of a cap layer and a grating layer brings a strong Fabry-Perot (FP) resonance as well as a weak guided mode (GM) resonance. Most of the reflected power results from the FP resonance, while the GM resonance plays a key role in achieving a reflectance close to 100% as well as broadening the stopband. An HG sample with 7 InGaAlAs quantum wells included in the cap layer has been fabricated by directly wafer-bonding a III-V cap layer onto a Si grating layer. Its reflection property has been characterized. This heterogeneously integrated HG reflector may allow for a hybrid III-V on Si laser to be thermally efficient, which has promising prospects for silicon photonics light sources and high-speed operation.

Near-field analysis of metallic DFB lasers at telecom wavelengths

We image in near-field the transverse modes of semiconductor distributed feedback (DFB) lasers operating at λ ≈ 1.3 μm and employing metallic gratings. The active region is based on tensile-strained InGaAlAs quantum wells emitting transverse magnetic polarized light and is coupled via an extremely thin cladding to a nano-patterned gold grating integrated on the device surface. Single mode emission is achieved, which tunes with the grating periodicity. The near-field measurements confirm laser operation on the fundamental transverse mode. Furthermore--together with a laser threshold reduction observed in the DFB lasers--it suggests that the patterning of the top metal contact can be a strategy to reduce the high plasmonic losses in this kind of systems.

In Situ Generation of Surface Plasmon Polaritons Using a Near-Infrared Laser Diode

We demonstrate a semiconductor laser-based approach which enables plasmonic active devices in the telecom wavelength range. We show that optimized laser structures based on tensile-strained InGaAlAs quantum wells-coupled to integrated metallic patternings-enable surface plasmon generation in an electrically driven compact device. Experimental evidence of surface plasmon generation is obtained with the slit-doublet experiment in the near-field, using near-field scanning optical microscopy measurements.

Ultrashort pulse generation from 156 µm mode-locked VECSEL at room temperature

We report on a picosecond pulse source delivering near transform-limited pulses in the 1.55 µm wavelength region, based on an optically pumped InP-based mode locked Vertical External Cavity Surface Emitting Laser (VECSEL). The cavity combines two semiconductor elements, a gain structure which includes six strained InGaAlAs quantum wells and a hybrid metal-metamorphic Bragg bottom mirror bonded onto a CVD diamond substrate, and a single quantum well GaInNAs SEmiconductor Saturable Absorber Mirror (SESAM). The laser operates at a repetition frequency of 2 GHz and emits near-transform-limited 1.7 ps pulses with an average output power of 15 mW at room temperature, using 1.7 W pump power at 980 nm. The RF line width of the free running laser has been measured to be less than 1 kHz.

Optical gain and threshold properties of strained InGaAlAs/AlGaAs quantum wells for 850-nm vertical-cavity surface-emitting lasers

The valence subband structures, optical gain spectra, transparency carrier densities, and transparency radiative current densities of different compressively strained InGaAlAs quantum wells with Al 0.3Ga 0.7As barriers are systematically investigated using a 6 × 6 k · p Hamiltonian including the heavy hole, light hole, and spin–orbit splitting bands. The results of numerical calculations show that the maximum optical gain, transparency carrier densities, transparency radiative current densities, and differential gain of InGaAlAs quantum wells can be enhanced by introducing more compressive strain in quantum wells. However, further improvement of the optical properties of InGaAlAs quantum wells becomes minimal when the compressive strain is higher than approximately 1.5%. The simulation results suggest that the compressively strained InGaAlAs quantum wells are of advantages for application in high-speed 850-nm vertical-cavity surface-emitting lasers.

Photoluminescence and X-ray diffraction studies of MBE-grown compressively strained InGaAs and InGaAlAs quantum wells for 1.55 μm laser diode applications

Compressively strained InGaAs and InGaAlAs multiple quantum wells were grown on InP by molecular beam epitaxy and their material qualities were investigated by double-crystal X-ray diffraction (DCXRD) and photoluminescence (PL). From the satellite peaks in a DCXRD scan, precise layer structures were determined. By comparing PL spectra of strained quantum wells having different well thicknesses, 75 Å thick quantum wells were found to be more suitable for laser diode applications than thinner wells. To achieve the required lasing wavelength of 1.55 μm with 75 Å wide strained quantum wells, quaternary InGaAlAs quantum wells were studied. It was also found that quaternary InGaAlAs strained quantum wells are less prone to strain relation than ternary InGaAs.

Large Quantum-Confined Stark-Effect in Quaternary InGaAlAs Quantum Wells

A large energy shift of excitonic absorption peaks in quaternary InGaAlAs quantum wells operating in the 1.5 µm wavelength region has been demonstrated in a waveguide configuration. Shifts of up to 30 meV (600 Å) and 17 meV (270 Å) have been achieved for the electron-to-heavy-hole and the electron-to-light-hole exciton absorption peaks, respectively. These shifts were obtained using a reverse bias of 6 V and without causing large broadening of exciton features. These values agree well with the calculated values.